KNOWLEDGE. 



[Januaky 2, 1899. 



interest -which arise from the brief narrative we have 

 given, and fi-om other facts which may be brought in 

 relation to it, and in doing so, we shall find it best to 

 consider the life-history of the organism in a different 

 order from that previously used. We started with the 

 sporangium, as the most easily grasped and the best known 

 stage of life ; but we shall now ask you to consider the 

 life-history bypassing from the simpler to the more complex 



SwAKii Spokes. — And first let us revert to the swarm 

 spores, those little bits of mere translucent protoplasm 

 which escape from the spores of the myxie (Pig. 3), leaving 

 the shells of the spores, from which they have emerged, 

 behind, as in Uke manner the spores leave behind them 

 the membrane of the sporangium. We have seen that in 

 some cases the myxies form a membrane or coat — as in 

 the sporangium, the spores, the microcysts, and the 

 sclerotium ; and it is probable that this membrane is in 

 some, though comparatively few, cases of the same or a 

 similar nature to the material of cell walls in the higher 

 plants, i.e., is formed of cellulose. But what is to be noted 

 is this, that these membranes are used only as protections ; 

 they are allowed no part or lot in the vital actions of the 

 organism, and, so soon as their protection is no longer 

 wanted, they are cast oft" and allowed to perish. It is 

 evident that the contained protoplast and not the containing 

 membrane is the dominant partner in the concern. 



A swarm spore has been defined as " a mobile, ciliated, 

 asexual, reproductive cell, destitute of all membrane," or, 

 in other words, it is a piece of protoplasm without any 

 covering membrane, which is produced without any sexual 

 action, and which of itself possesses the powers of motion, 

 of putting out cilia or hairs, and of joining in the repro- 

 duction of the species to which it belongs. That all this 

 should be true of a little bit of jelly is marvellous enough, 

 and presents some of the mysteries of life in a very simple 

 and condensed form. 



Swarm spores, in the sense of the preceding definition, 

 are common in both the great kingdoms of organized life. 

 There is a whole group of protoplasts which, under the 

 name of Monads, are reckoned to belong to the animal 

 kingdom ; there is the group of somewhat larger organisms 

 known as " Amosbce " — a group of which a suspicion has 

 sometimes been entertained that they are an immature form 

 of other organisms ; there are the white particles of the 

 blood which are almost, if not quite undistinguishable 

 from Ama?bcB ; there are the swarm spores, whether 

 belonging to the Algn?, the Fungi, or the Myxomycetes; in 

 all these cases the protoplasts are of the same kind, 

 endowed with nuclei and vacuoles, capable of putting out 

 cilia, and endowed with the power of motion and assimila- 

 tion. To all appearances there is no essential difi'erence 

 between them, and yet, in point of fact, they are organisms 

 as distinct as possible from one another in their nature and 

 their future careers. 



One thing marks off the swarm spores of the myxies 

 from all other swarm spores which reproduce the organism ; 

 they are reproductive only in conjunction. The swarm 

 spore of an alga is capable by itself of reproducing an alga ; 

 in the myxies, on the other hand, the swarm spores only 

 reproduce when they have merged with their fellows and 

 formed a Plasmodium. This phenomenon of the union of 

 a large number of individual swarm spores into a new and 

 larger individual which carries forward the course of life 

 is unique in the myxies, and distinguishes them broadly 

 from all other known organisms. 



In all cases in which reproduction depends on swarm 

 spores it seems essential that there should be water 

 enough for the swarm spores to live and move about in ; 



and, in the case of myxies, to enable them also by their 

 : movements to join together into a plasmodium. Nothing 



is known of their reproduction except in water. 

 \ It would at first sight appear that this condition of 

 ' their reproductive activity cannot be otherwise than in- 

 convenient and restrictive, especially in the case of such 

 myxies as, e.i/., the Comatrich», which often produce their 

 sporangia on the upper sides of wood, or on the tops or 

 sides of wooden posts. But it is probable that a very little 

 moistm-e is enough, and that in a shower of rain, or Ln a 

 morning's dew, they find sufficient water for the swarm 

 spores to live and unite. But we confess that the point 

 seems to us to require further attention. 



Water being the medium in which most of the lowest 

 organisms exist, it is generally thought that the doctrine 

 of evolution involves this — that the earth has been peopled 

 by migrations from the water ; and the migrations of 

 amphibious animals from the one element to the other 

 have been dwelt on as assisting us to understand such 

 migration. In this connection the cases of the myxies 

 and of the mosses, and no doubt of other mainly terrestrial 

 organisms which need water as a necessary condition to 

 fertilization, are worthy of note. One of the most important 

 functions of life still depends on the presence of the original 

 medium of their lives. 



Cell Theory. — The swarm spore is, as we have said, 

 a bit of naked protoplasm ; so is the plasmodium. Let us 

 consider briefly what is meant by the expression naked 

 protoplasm. 



When in the seventeenth century the microscope was 

 applied to vegetable tissues, especially by our countrymen 

 Hooke and Grew, and by the Italian Malphigi, they were 

 struck with the presence of small walled cavities in the fieshy 

 parts of plants. These Hooke called cells, and Grew and 

 Malphigi utricles or bladders. Hooke's name has stuck to 

 them, and plays a great part in botanical writings from 

 his day to the present. We are accustomed to regard the 

 cell division as the determining factor in growth, the mode 

 of division providing, as it were, the form which the plant 

 is to assume : and especially since the days of Schleiden 

 and Schwann — when the cell came to be regarded as the 

 structural unit in the growth of plants — the tracing of 

 cell development, and the structure of the parts of the cell 

 (especially the cell walls), and the behaviour of the cell, have 

 been studied with the utmost care. Presently it came to be 

 seen that the cell walls were inert and by no means the most 

 important part of the structure, but that the slimy contents 

 of the little box, which had been treated with scant atten- 

 tion in the earlier stages of study, were, after aU, the most 

 remarkable part of the cell, and were to all appearance the 

 basis of both animal and vegetable life. When attention 

 was first called definitely to it in the vegetable kingdom it 

 was termed protoplasm, by Mohl ; when first accurately 

 observed in animals it was named sarcode by Dujardin ; 

 and by-and-by it was found that protoplasm and sarcode 

 were one and the same thing. Then instances were 

 found in which small masses of protoplasm lived and 

 moved without any cell walls at all, but so firmly 

 was the notion of the cell rooted in the minds of many 

 physiologists, that these naked pieces of protoplasm 

 have often been called naked cells, a most confusing term 

 as it seems to us, for it is like calling a man with nothing on 

 " a naked great coat." Another name, and a much more 

 convenient one, is protoplast. 



The accepted cell theory received something like a shock 

 when the life-history of the myxies came to be carefully 

 studied. " All the phenomena," said Cienkowski, in the 

 year 1S63, " which are observed in plasmodia are calculated 

 to force the observer from the accustomed path of safety 



